1. Field of the Invention
This invention concerns the field of coating strands, for example, wires with a polymer.
2. Description of Related Publications
Methods for coating strands (e.g. wires) includes several methods, including the use of extrusion or coextrusion techniques. In the extrusion technique, a tube is made for the wire to be coated through which the wire can later be slipped. In coextrusion, a urethane material, for example, is applied directly to the wire being covered. Both of these methods involve the use of heat to melt the polymer and high pressure to push the rather highly viscous material out of the extrusion orifice. These processes have limitations in that the thickness of the urethane coating being applied must be relatively great to achieve uniformity and a smooth defect-free finish. Therefore, such techniques are not very useful when one wants to apply a coating only a few one-thousandths of an inch thick since close tolerance between orifice and wire diameters is required.
Urethanes are also adaptable to vacuum and injection molding systems. Again, like extrusion, high temperature melting is required and the adaptability of such techniques for small wire coating is severely limited.
Another technique called "lacquering" is used for coating wire or other materials. In this technique, the urethane is dissolved in a volatile solvent and then the resultant solution is sprayed on the object to be coated. Alternately, the object is dipped into the solution for coating much as one would make candles. The solvent is then evaporated at temperatures up to 200.degree. C. leaving an adherent film of urethane to harden on the surface. This latter technique is disadvantaged since the process is slow and provides only limited production possibilities. In addition, because the urethane lacquers are quite thin when applied, they tend to run off or sag on the surface to be covered.
U.S. Pat. No. 4,497,849 describes such techniques and suggests improvements.
U.S. Pat. Nos. 4,396,729; 4,444,910 and 4,433,067 concern elastomers prepared using a high molecular weight amine terminated polyether, an aromatic diamine chain extender and an aromatic polyisocyanate which may merely be a polyisocyanate or a quasi-prepolymer prepared from a polyol reacted with a polyisocyanate wherein some isocyanate groups are still left unreacted. Various patents have been applied for and received using the basic combination recited above as well as various mold release agents and other additives, for example, catalysts.
European Pat. Application No. 81,701A concerns reaction injection molded elastomers where fatty acid salts are recommended internal mold release agents. The corresponding U.S. application Ser. No. 443,444, filed 11/2282, is the subject of interference proceedings with the '729, '910 and '067 patents referred to above (Interference Nos. 101,393; 101,394; and 101,395).
U.S. Pat. No. 4,585,850 concerns and claims a reaction injection molded elastomer made by reacting in a closed mold amine terminated polyethers of greater than 1500 average molecular weight, having greater than 50% of their active hydrogens in the form of amine hydrogens, a chain extender, flaked glass pretreated with amino silane coupling agent, and an aromatic polyisocyanate. The '850 patent referred to above contains a discussion of other applications and patents in the field; for example, U.S. Pat. No. 4,474,900 and U.S. Pat. No. 4,507,090, and is incorporated herein by reference.
European Pat. Application No. 81,701A concerns reaction injection molded elastomers where fatty acid salts are recommended internal mold release agents. The corresponding U.S. application Ser. No. 443,444, filed 11/22/82, is the subject of interference proceedings with the '729, '910 and '067 patents referred to above (Interference Nos. 101,393; 101,394; and 101,395)
The paper "Silane Effects and Machine Processing in Reinforced High Modulus RIM urethane Composites," by E. G. Schwartz, et al., Journal of Elastomers and Plastics, vol. 11 (Oct. 1979), page 280, describes the use of silane treated milled glass fibers in reinforced RIM composites.
The article "Surface Modification for RRIM Urethanes," by Ed Galli, Plastics Compounding (Jan/Feb 1982) discloses silane treated glass fiber reinforcement of RRIM urethanes. The emphasis is on amino silanes.
By use of the formulations disclosed in the above patents, for example U.S. Pat. No. 4,433,067, a rapid way to coat strands of various materials is provided. Unlike the citations in the '850 patent above and the journal articles referred to above, the present invention describes a method for coating strands of various materials whereas those references discuss the use of filler materials, for example, glass fibers in the formulation. The present invention describes a method for coating strands of various materials by spraying onto the strands a formulation similar to that described in U.S. Pat. No. 4,433,067 and claimed hereinafter.